Dual-polarized dipole array antenna

ABSTRACT

An improved dual-polarized dipole antenna has two orthogonal parallel dipoles of a dipole square fed by a feeder point on one of the dipoles. Starting from said feeder point, a connection cable to the feeder point on the respective orthogonal parallel dipole of the dipole square is laid and is electrically connected there to the dipole halves of the dipole square.

CROSS-REFERENCES TO RELATED APPLICATIONS

Not applicable.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

FIELD

The technology herein relates to a dual-polarized dipole antennaaccording to the preamble of claim 1.

BACKGROUND AND SUMMARY

As shown in DE 198 23 749 A1 (see also U.S. Pat. No. 6,333,720, entitled“Dual-Polarized Multi-Range Antenna”), a dual-polarized dipole antennahas become known which is suitable for mobile radio networks usedthroughout the world, particularly the GSM900 or GSM1800 network fortransmission in the 900 MHz or 1,800 MHz band.

A generic dual-polarized antenna which has become known uses apolarization orientation of ±45°. The antenna includes a number ofdipole squares in a joint antenna housing in front of a reflector. Anumber of such dipole squares are usually arranged in the verticaldirection for transmitting in one frequency. A further different dipolesquare is provided for transmitting in the other frequency band. Forexample, the different dipoles may be arranged between two such dipolesquares arranged vertically above one another.

The horizontal half-power beam width of the antenna, which is mainlyused, is 65°. To make antenna as compact as possible, two single dipolesare often connected together with the same phase in order to achieve the65° half-power beam width for each polarization. The dipoles areoriented at +45° and −45°, respectively. This results in a so calleddipole square,

The two horizontal radiation patterns of the +45° and −45° polarizationsshould be oriented to be coincident, if possible. Any deviation iscalled tracking.

To achieve a narrower vertical half-power beam width and to increase theantenna gain, a number of dipole squares are often connected together inthe vertical direction. If this is done in phase, the two antennaspolarized by +45° and −45° do not have any electrical depression. Withan antenna dimensioned and arranged like this, there is no or onlyminimal tracking. The cross-polarized components of the radiationpattern are also minimal.

Today, it is mainly the ±60° sector which is of significance for mobileradio. In recent years, mobile networks have become ever more dense dueto the great success of mobile radio. The existing frequencies must beused more economically at closer and closer distances. It the coverageis too dense, interferences are produced. A remedy can be achieved byusing antennas having a greater electrical depression, for example adepression angle of up to 15°. However, this has the unpleasant sideeffect that as the depression angle increases, the two horizontalpatterns of the dual-polarized antennas drift apart, i.e. the horizontalpattern polarized +45° drifts in the positive direction and thehorizontal pattern polarized −45° drifts in the negative direction. Thisleads to considerable tracking with large depression angles.Furthermore, the tracking is frequency-dependent. Similarly, thecross-polarized components of the radiation pattern follow thehorizontal patterns which leads to a distinct deterioration in thepolarization diversity characteristics in the ±60° sector.

It is, therefore, desirable to overcome the disadvantages of the priorart and create an improved dual-polarized antenna.

Using comparatively simple means in the generic dual-polarized dipoleantenna, even with a comparatively great depression, it is possible toachieve horizontal patterns do not drift apart or, at least, thedrifting-apart is distinctly minimized. On the other hand, the solutionaccording to the exemplary non-limiting illustrative implementation alsoprovides possibilities to achieve a particular tracking, if required,for example in the case of a non-depressed radiation pattern. Theresultant improved compensation for the tracking in dependence onfrequency is surprising.

Due to the fact that the tracking is eliminated or at least minimized inaccordance with the exemplary non-limiting illustrative implementation,the cross-polarized components of the radiation pattern are alsodistinctly improved. As a consequence, the polarization diversitycharacteristics are also improved.

A further advantage is also that the overall expenditure of cables canbe reduced compared with conventional antenna installations.

The surprising solution according to the exemplary non-limitingillustrative implementation is based on the fact that two oppositeparallel dipoles of a dipole square which radiate or, respectively,receive with the same polarization are not fed in parallel or withbalanced cables or with separate cables. Rather, the feeding takes placeonly with respect to one dipole, and a connecting cable is then providedfrom the feed point at one dipole to the feed at the opposite second,parallel dipole.

Due to the feeding arrangement according to the exemplary non-limitingillustrative implementation, orienting the radiators to +/−45° causes afrequency-dependent squinting of the dipole squares and thus also adrift of the patterns in the horizontal and in the vertical direction.It is completely surprising that this leads to a wide-band improvementin the tracking and additionally reduces the cross-polarized componentswithout impairing the electrical depression. This is all the moresurprising as the interconnection of the dipoles according to theexemplary non-limiting illustrative implementation results in a mostunwanted narrow-band characteristic of the antenna from the point ofview of conventional wisdom and, in addition, a disadvantageousfrequency-dependence of the depression angle would be expected.

In a preferred implementation of the exemplary non-limiting illustrativeimplementation, the electrical length of the connecting cablecorresponds to one wavelength λ or an integral multiple thereof referredto the center frequency to be transmitted.

Such antennas usually do not comprise only one dipole square but anumber of dipole squares arranged, as a rule, above one another in thevertical direction of installation and aligned at a 45° angle to thevertical. Using the present exemplary non-limiting implementation, thetracking can now be preset differently in accordance with therequirements. In a preferred implementation of the exemplarynon-limiting illustrative implementation, this can be effected, forexample, by feeding, from the feed cable, only at the same side ofdipoles aligned with the corresponding polarization and, connectingcables leading to the opposite dipole in the same manner for alldipoles.

A change in the amount of tracking, however, can be implemented by thefact that, for example, the feeding of four dipole squares arranged oneabove one another takes place with reference to the dipole on the leftin three dipole squares with respect to the dipoles arranged in parallelwith one another. Only with respect to one dipole square does it takeplace only with respect to the dipole parallel thereto on the right inan exemplary non-limiting implementation.

If, for example, with reference to four dipole squares, the feeding isonly effected at the dipoles on the left in the case of two dipoles andthe other half of the feeding is effected only at the dipoles on theright (the feeding with respect to the in each case second paralleldipole taking place via the connecting line), a different value isobtained for the tracking.

The degree and magnitude of the compensation value for thedrifting-apart of the +45° and −45° polarized horizontal patterncomponent can be set correspondingly finely and compensated for. Adifferent proportion is used which in the case of two dipoles orientedin parallel with one another, initial feeding takes place and a dipoleis fed via a connecting line coming from there.

In the field of the dual- or cross-polarized antenna, the series feedwhich can be selected differently if necessary, and can be used forcompensating for the frequency-dependence of the radiation patterns andfor compensating for the tracking. This is completely surprising and notobvious.

The solution according to the exemplary non-limiting illustrativeimplementation also provides the further advantage that only one feedcable, provided with a cross section of correspondingly large dimension,to in each case two dipoles located offset by 90° is provided. Fromthese two dipoles, in each case only one connecting cable, provided witha thinner cable cross section, is conducted to the opposite dipole of adipole square. This distinctly reduces the overall cable expenditure.

BRIEF DESCRIPTION OF THE DRAWINGS

Further advantages and details of the exemplary non-limitingillustrative implementation are found in the example explained in thetext as shown in the drawings, of which:

FIG. 1 shows an exemplary non-limiting dual-polarized dipole antennaimplementation comprising a number of dipole squares;

FIG. 2 shows a diagrammatic side view of an exemplary dipole squarealong the direction of arrow A in FIG. 1 with cabling according to theprior art;

FIG. 3 shows a top view of the dipole square of FIG. 2 of the prior art;

FIG. 4 shows a diagrammatic side view of an exemplary dipole squarealong the direction of arrow A provided by an exemplary non-limitingillustrative implementation of the technology herein; and

FIG. 5 shows a top view of the exemplary implementation according toFIG. 4;

FIG. 6 shows a diagrammatic representation of an exemplary non-limitingimplementation of eight dipole squares, arranged vertically above oneanother and rotated by 45° inclination, with differently located feedpoints; and

FIG. 7 shows a further exemplary implementation, slightly modified, withsix dipole squares arranged above one another and with differentlylocated feed points.

DETAILED DESCRIPTION

FIG. 1 shows a diagrammatic top view of an exemplary non-limitingimplementation of dual-polarized dipole antenna 1 having a number offirst dipole squares 3 and a number of second dipole squares 5. Thefirst dipole squares 1 are used, for example, for transmitting in the900 MHz band, The second dipole squares 5 of comparatively smallerdimensions are tuned, for example, for transmission in the 1,800 MHzband. All dipole squares 3 and 5 are oriented inclined by 45° withrespect to the vertical and horizontal and arranged along a verticalmounting direction 7 above one another in front of a reflector 9 at asuitable distance in front of the reflector plate 9′.

With respect to the basic configuration and operation, reference is madeto the previously published prior art according to DE 198 23 749 A1(U.S. Pat. No. 6,333,720) to the content of which reference is made inits full extent and which is incorporated as content of the presentapplication.

These dipole squares, which are basically previously known, have aconfiguration and a feed according to FIGS. 2 and 3 of the presentapplication.

The dipole squares in each case comprise two pairs of parallel dipoles13 and 15 which, according to the top view of FIG. 4, are arranged inthe manner of a dipole square. Both dipole pairs 13′ and 13″ and the twodipole pairs 15′ and 15″ are carried and held via a balancingarrangement 113′ and 113″ and, respectively, 115′ and 115″ which, in theexemplary implementation shown, extend from a base and anchoring area 21on the reflector 9 with a vertical and in each case outwardly pointingcomponent to the dipole halves located at a distance in front of thereflector 9. A first connecting cable 31 (coaxial cable) is conducted,usually via a hole 23 in the reflector 9, from a feed cable 27 comingbehind the reflector 9 in the area of the base point or the anchoringarea 21 via a branching point 29 along one support arm of the balancingarrangement 113 to the feed point 33 at which the external conductor 31a is electrically joined, for example to the support arm 113′. Theinternal conductor 31 b is constructed, separately from this, extendedin the axial longitudinal direction over a small distance and iselectrically connected to a connecting point or elbow 35 connected tothe second dipole half.

The same joining connection is made for the opposite dipole. Theelectrical feed to the two dipole pairs, located offset by 90°, whichare not drawn in FIGS. 2 and 3 for the sake of clarity, is effected viaa separate second feed cable and two further separate connecting lines.

By comparison, according to the exemplary non-limiting illustrativeimplementation, a feed according to FIGS. 4 and 5 is now carried out inwhich the feed cable 27 (e.g. coaxial cable) is conducted directly tothe feed point 33 at a dipole. The feed cable 27 is there againelectrically connected to the feed point 33′ (which is connected to onedipole half) with its internal conductor, and the external conductor 31b is electrically connected to the other dipole half at feed point 33′.

From this feed point 33, a connecting cable 37 leads to the feed point35 at the opposite dipole half. In this exemplary non-limitingarrangement, the inner conductor is again electrically connected to onedipole half via the connecting point 35′ and the outer conductor isconnected to the second dipole half at 35″.

In practice, the feed cable is also run here, via the hole 23 at onesupport arm or in one support arm of the balancing arrangement 113′ or113″ (if this is constructed, for example, as a waveguide or hollowsupport) in the interior and conducted to the feed point 33. At feedpoint 33, the outer conductor is electrically connected to one dipolehalf and the inner conductor is connected to the connecting point of thesecond dipole half. The coaxial connecting cable 37 is similarlyconducted back again in the direction of the reflector plate 9′ from thefeed point 33 at one dipole at or, for example, in the second supportarm 113′ or 113″ of the corresponding balancing arrangement 113. Thecable 37 may for example be conducted in the possibly hollow support armof the opposite balancing arrangement 113 of the opposite dipole 13′ toits feed point 35 located at the top.Alternatively, it can be run at thebalancing arrangement or in another suitable manner. FIGS. 1, 4 and 5show the principle of interconnection which is why the respective feedcable 27 is shown conducted to the feed point coming virtually from theoutside although, in practice, it is conducted along the balancingarrangement to the feed point 33 coming via the central hole 23.

In one exemplary implementation, the length of the connecting cableshould be λ or an integral multiple thereof referred to the frequencyrange to be transmitted, particularly the center frequency range.

Correspondingly, the feeding to the two dipoles 15 and 115, locatedoffset by 90° in the exemplary implementation of FIGS. 4 and 5, iscarried out via a separate feed cable or a corresponding separateconnecting cable. There, too, a feeding via a separate feed cable takesplace first at one dipole 15′ and at a feed point constructed there.From there, a separate connecting cable is then conducted to an oppositedipole 15″ and connected to a corresponding feed point.

FIG. 1 shows by way of example that the dipole halves 13′ and 15′ (shownlocated on the left in each case), are fed there at a corresponding feedpoint 35 via two separate feed cables 27. Connecting cables 31 lead fromthere to the in each case opposite dipoles 13″ and 15″, respectively, tofeed points provided there.

Thus, for example, all dipole squares 3 which are larger in FIG. 1, butalso all smaller dipole squares 5, can be fed in the same manner.

It is also possible that, for example, a single dipole square or, in thecase of even more dipole squares arranged above one another vertically,for example one half or any other combination of dipole squares are feddifferently. Thus, it is shown, for example with respect to the lowestdipole square 3 in FIG. 1, that feeding takes place via two separatefeed cables at the dipoles on the right in the dipole square(namely atdipole 13″ and dipole 15″, at the feed points explained). The feeding atthe opposite parallel dipole is then, in one exemplary arrangement,carried out in each case starting from the first feed point via twoseparate connecting lines 31.

Depending on whether the first feeding takes place and which of thedipoles, which are in each case parallel in pairs, of a dipole square isconnected electrically by the connecting line starting from the firstdipole, a different measure of the tracking is also obtained.

FIGS. 6 and 7 show two illustrative non-limiting examples of one set ofeight dipole squares arranged one above another in 45° orientationwhich, to achieve a quite particular value for the tracking, exhibitdifferent feeding with respect to the dipoles on the left or withrespect to the dipoles on the right. This correspondingly applies to theexemplary implementation according to FIG. 7 which shows six dipolesquares arranged above one another in 45° orientation. The feeding forthe various dual-polarized dipole squares is implemented starting ineach case from a main feed line 27 via subsequent distributors and taps.The reflector plate of FIG. 1 is not shown in FIGS. 6 and 7 for the sakeof clarity.

While the technology herein has been described in connection withexemplary illustrative non-limiting implementations, the invention isnot to be limited by the disclosure. The invention is intended to bedefined by the claims and to cover all corresponding and equivalentarrangements whether or not specifically disclosed herein.

What is claimed is:
 1. A dual-polarized dipole antenna comprising: atleast one dipole square oriented rotated at a 45° angle with respect tothe vertical or horizontal, said dipole square including first andsecond opposite parallel dipoles; a feed cable connected to a feed pointat the first dipole; and a connecting cable run to the feed point at thesecond, opposite parallel dipole of the dipole square and electricallyconnected to the dipole halves of the dipole square.
 2. The antenna asclaimed in claim 1, further comprising: two separate feed cables forsaid dipole square, the two feed cables leading to the feed points oftwo dipoles located offset by 90°, and separate connecting lines leadingfrom said feed points to further feed points on respective oppositeparallel dipole.
 3. The antenna as claimed in claim 1, furthercomprising plural dipole squares arranged above and/or next to oneanother along a direction of installation, the feed points connected tothe feed cables being located at a correspondingly common points ororientations at each of said dipole squares.
 4. The antenna as claimedin claim 1, further comprising plural dipole squares arranged above andnext to one another along a direction of installation, which feed pointsconnected to the feed cables are located at the respective other one ofthe dipoles parallel with one another in pairs.
 5. The antenna asclaimed in claim 1, further comprising support arms of dipole balancingarrangements, and wherein connecting lines are run from a first feedpoint at one dipole to a further respective feed point at the dipoleparallel thereto at or within the support arms.
 6. The antenna asclaimed in claim 5, wherein the connecting cables have different linecross sections.
 7. The antenna as claimed in claim 1, wherein areduction in the frequency-dependence of the orientation of the copolarand/or cross polar radiation patterns (tracking) is obtained independence on the feeding arrangement at each dipole square.
 8. Adual-polarized dipole antenna comprising: at least one dipole squarefor, in use, being disposed at an orientation that is rotatedsubstantially at a 45° angle with respect to vertical and horizontal,said dipole square comprising plural first dipoles located offset andopposite the square and parallel with respect to one another and pluralfurther dipoles located offset and opposite the square and parallel withrespect to one another, one of said first dipoles including a feedpoint; a coaxial feed line connected to said first dipole feed point;and a coaxial connecting line connected from the first dipole feed pointto a further one of the first opposite parallel dipoles to electricallyconnect dipole halves of the dipole square, wherein the electricallyeffective length of the coaxial connecting line is chosen such that therespectively opposite parallel dipoles are excited in phase.
 9. Theantenna of claim 8 wherein the electrically effective length of thecoaxial connecting line is at least approximately an integral multipleof wavelength λ with respect to the frequency band range to betransmitted.